The present invention relates to a control method and apparatus in purging to an engine, a fuel vapor recovered in an automobile fuel vapor recovering device, and preferably to a fuel injection control method and apparatus.
It is known that a fuel vapor generated from an automobile fuel tank reacts with an ultraviolet radiation to generate a photochemical smog, causing air pollution. Accordingly, in most countries, an emission quantity of the fuel vapor from an automobile is regulated to a given value to prevent environmental disruption.
As means to cope with the regulation of the emission quantity of the fuel vapor, an automobile fuel vapor recovering device as described in Japanese Patent Laid-open No. Sho 57-86555 is generally known. In such a conventional automobile fuel vapor recovering device, a purge rate is controlled to a fixed value, and a canister purge valve is controlled so as to follow a change in air quantity passed through a throttle valve.
To control the purge rate to the fixed value, the canister purge valve may be controlled so as to follow the change in throttle valve passing air quantity, Qtvo. However, in the case that the canister purge valve is a stepping motor type of canister purge valve, there is a problem in responsiveness of the canister purge valve, and it is difficult to control the purge rate to the fixed value.
It is accordingly an object of the present invention to solve such a problem in the prior art and provide a canister purge control method and apparatus for an internal combustion engine with good responsiveness.
A further object is to suppress an undue fluctuation in air-fuel ratio occurring upon rapid fluctuation in purge quantity in purging to an engine a recovered fuel vapor in an automobile fuel vapor recovering device.